Various techniques exist for the sterile welding of plastic tubes. Particularly noteworthy techniques are described in U.S. Pat. No. 4,793,880 of which I am a co-patentee. Other patents disclosing welding or sealing techniques for plastic tubes include U.S. Pat. Nos. 4,753,697; 4,770,735; 4,832,773; 4,864,101; 4,897,138; 4,913,756 and 4,933,036. In each of these patents I am a co-patentee with Dudley W.C. Spencer. Further patents of Dudley W.C. Spencer which are pertinent are U.S. Pat. Nos. 4,369,779; 4,412,835; 4,507,119; 4,516,971; 4,610,670 and 4,619,642.
While the above patents disclose variations of techniques for the sterile welding or sealing of plastic tubes, they focus primarily on the welding or sealing processes. With the advent of AIDS, the safe handling of dangerous biological fluids and safeguarding the nation's blood supply has assumed major significance. It would be desirable for example, for blood processing centers to be able to handle blood separations without the risk of exposure to the technician, CAPD patients need to be able to safely bag-off and bag-on, to automatically seal the discarded bag, or to be able to take a sample during bag-off for lab analysis. Hospital personnel need a way to avoid Hepatitis when changing urinary drainage bags. Farmers could inject a known quantity of reagent such as an insecticide into a closed system without fear of exposure from concentrates. Monitoring samples need to be safely taken from bioreactors and needed reagents or nutrients injected without fear of contamination. Filter, and other types of process modules need to be sterilely installed or removed.
Except for U.S. Pat. No. 4,753,697 the prior art does not address the problem of total containment of the tube contents. Even that patent is silent on anything other than welding one stub end to the other to effectively seal off the stubs. None of the other existing technologies can address all of these needs without an awkward double or triple welding step. Since they require a multi-step procedure, there exists a very high risk of mistakenly welding the wrong tubes together. During all the handling, the lightly tack-sealed stub-ends run a very large risk of leaking, contaminating both the operator and the system.